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41.
Palynomorph assemblages have been recovered from deposits believed to straddle the Ordovician/Silurian boundary, from the upper member of the Salar del Rincón Formation, in the Puna region of north-west Argentina. The palynomorph assemblages are dominated by terrestrial cryptospores, but also contain marine elements (acritarchs, prasinophycean algae and chitinozoans). The cryptospore assemblages are similar in composition to those described from coeval deposits worldwide, suggesting that the producers were cosmopolitan and tolerated a wide range of climatic conditions. They are correlated with the Imperfectotriletes spp. Interval Biozone (sub-biozone α) of the Imperfectotriletes spp.- Laevolancis divellomedia Assemblage Biozone, indicating a Hirnantian (latest Ordovician) age. Acritarchs include late Ordovician species such as Eupoikilosusa striata and Villosacapsula cf. setosapellicula , that coexist with the Llandovery species Dactylofusa estillis. Based on lithological and palynological evidence, an early Llandovery, or a late Hirnantian (post-glacial) age is proposed for the basal part of the upper member of the Salar del Rincón Formation. 相似文献
42.
Jisuo Jin 《Palaeontology》2003,46(5):885-902
Eocoelia akimiskii sp. nov. from the Lower Silurian (upper Telychian) Attawapiskat Formation of Akimiski Island, James Bay, Nunavut, is the first and oldest Eocoelia to be described from the Hudson Bay Basin, one of three largest inland basins of North America. The new species lacks dental plates, dental cavities, and marginal deflection or lip, which indicates a post-Aeronian form of the well-known Eocoelia lineage. In rib numbers, Eocoelia akimiskii falls between E. curtisi and E. sulcata , being closer to E. sulcata . In rib strength, however, the new species is more closely allied to E. curtisi . Although Eocoelia is currently assigned to the Rhynchonellida because of its lack of spiralia, several features (particularly the lack of a septalium, the presence of a unique notothyrial platform and cardinal process, and dense, free-hanging fibrous growth frills) of the genus and other leptocoeliids are distinctly atypical of the rhynchonellides. The new species occurs in an inter-reef, shelly packstone facies within the Attawapiskat Formation, which is characterized by coral-stromatoporoid reefs with abundant, diverse, reef-dwelling brachiopods and other shelly organisms. The close association of Eocoelia akimiskii with the Attawapiskat reefs supports a shallow subtidal (BA2) setting generally assigned to the Eocoelia Community. The reefs themselves, however, host an extremely abundant brachiopod fauna dominated by Pentameroides , Trimerella , Septatrypa , and Gypidula . Four species of Clorinda are also common elements of the reef-dwelling brachiopods. This demonstrates that the concept of the classic Early Silurian level-bottom brachiopod communities cannot be directly applied to reef-dwelling brachiopod communities. 相似文献
43.
Carbonized grains of sorghum, with consistent radiocarbon dates of ca. 8000 B.P., have been excavated at an early Holocene archaeological site (E-75-6) in Nabta Playa near the Egyptian-Sudanese border. The objective of the investigations reported here was to classify these early sorghum grains within the known wild or domesticated races or working groups of sorghum through the use of image-analysis procedures. Image-analysis is a non-destructive analytical method that can provide rapid, repeatable, and accurate measurements of ancient cereal grains. Measurements were taken on samples representing the five major domesticated sorghum races, eight wild relatives, and samples from the Nabta Playa and Jebel et Tomat excavation sites. Statistical and clustering techniques indicated significant differences existed among the sorghums with respect to the various measurements made. Sorghum from Nabta Playa was significantly smaller, with respect to most measurements, than either the wild relatives or the five cultivated sorghums. Smaller grain size and the lack of any spikelets containing attached branchlets of the inflorescence or rachis fragments suggest that the material harvested and eaten at the Nabta Playa site were of a wild type. 相似文献
44.
Evidence for plant exploitation and vegetation history from three Early Neolithic pre-pottery sites on the Euphrates (Syria) 总被引:3,自引:0,他引:3
George Willcox 《Vegetation History and Archaeobotany》1996,5(1-2):143-152
Archaeobotanical results based on a limited number of samples from three aceramic sites dating from 9800 to 7800 B.P., which
are under excavation in the valley of the Middle Euphrates, are discussed. The finds are presented simply by presence, and
are compared to the contemporary vegetation and finds from similar sites. Carbonised plant remains recovered by flotation
from levels dated to between 9800 and 9200 B.P. (Dja'de and Jerf al Ahmar) indicate that wild cereals (einkorn wheat, rye
and barley) and pulses (lentils, pea and bitter vetch) were exploited. Other plants such as wild grasses, Pistacia, wild almond and oak, suggest that the local vegetation provided a rich diversity of resources. A study of possible weed
taxa is being carried out in order to see whether this assemblage could be used to identify the cultivation of morphologically
wild cereals for this period. Ninth millennium B.P. levels at Halula see the appearance of domestic crops such as emmer, naked
wheat and barley, but wild-type cereals persist. The cultivars appear to have been introduced from elsewhere and later ninth
millennium B.P. species include olive and flax. Ash, vine, maple, plane, alder and elm from the gallery forest, wild rye,
wild einkorn, deciduous oak, wild almond, Pistacia, and Pyrus, from the hinterland, indicate cooler conditions. 相似文献
45.
Hermann Behling 《Vegetation History and Archaeobotany》1996,5(3):241-246
Palynological studies on late Quaternary lake sediments from the region of the Amazon estuary, 100 km north-east of Belém, Pará State, Brazil, enable reconstruction of lowland Amazonian rain forest during the Late-glacial and Holocene periods. Late-glacial forests included populations of Podocarpus which suggests a distinct climatic cooling. Ilex was abundant in the early Holocene. Records of the mangrove taxon, Rhizophora, indicate rapid Atlantic sea-level rise in the beginning of the Holocene. High charcoal representation may reflect the first arrival of Amerindians in the Amazon coastal area, probably about 10 800 B.P. 相似文献
46.
H. Ü. Kolukisaoglu S. Marx C. Wiegmann S. Hanelt H. A. W. Schneider-Poetsch 《Journal of molecular evolution》1995,41(3):329-337
Thirty-two partial phytochrome sequences from algae, mosses, ferns, gymnosperms, and angiosperms (11 of them newly released ones from our laboratory) were analyzed by distance and characterstate approaches (PHYLIP, TREECON, PAUP). In addition, 12 full-length sequences were analyzed. Despite low bootstrap values at individual internal nodes, the inferred trees (neighbor joining, Fitch, maximum parsimony) generally showed similar branching orders consistent with other molecular data. Lower plants formed two distinct groups. One basal group consisted of Selaginella, Equisetum, and mosses; the other consisted of a monophyletic cluster of frond-bearing pteridophytes. Psilotum was a member of the latter group and hence perhaps was not, as sometimes suggested, a close relative of the first vascular plants. The results further suggest that phytochrome gene duplication giving rise to a- and b- and later to c-types may have taken place within seedfern genomes. Distance matrices dated the separation of mono- and dicotyledons back to about 260 million years before the present (Myr b.p.) and the separation of Metasequoia and Picea to a fossil record-compatible value of 230 Myr B.P. The Ephedra sequence clustered with the c- or a-type and Metasequoia and Picea sequences clustered with the b-type lineage. The paleoherb Nymphaea branched off from the c-type lineage prior to the divergence of mono- and dicotyledons on the a- and b-type branches. Sequences of Piper (another paleoherb) created problems in that they branched off from different phytochrome lineages at nodes contradicting distance from the inferred trees' origin.
Correspondence to: H.A.W. Schneider-Poetsch 相似文献
47.
48.
中国下泥盆统脊椎动物化石组合层序 总被引:8,自引:4,他引:4
本文综合了滇、黔、川、桂等地的一些早泥盆世地层剖面中的脊椎动物化石的出露情况,粗略地描绘出了早期脊椎动物演化的一般特征,归纳成三个发展阶段。并以此为依据,讨论了下泥盆统的分层与对比。 相似文献
49.
J A Wallace 《American journal of physical anthropology》1977,46(3):483-493
Gingival eruption of the permanent teeth of Australopithecus, Paranthropus, and early Homo, diagnosed from enamel scratches and facets, is similar save for two sequences: eruption of the canines relative to the premolars which may be sexually dimorphic; and agenesis of M3 with delayed eruption of M2, first seen in Homo at two million years. Gingival eruption sequences are similar also for early and modern Homo, except that in some individuals today M3, M2, M1 and I2 take longer to form and emerge through the gingiva as functioning teeth. Probably, from two million years to the present in the evolutionary history of Homo dental development slowed-down. More and more of ontogeny has been taken over for eruption. 相似文献
50.
Recent freshwater oscillatoriacean analogue of the Lower Palaeozoic calcareous alga Angulocellularia
ROBERT RIDING LARISA VORONOVA 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1982,15(2):105-114
Recent freshwater cyanophyte oncoids from Canandaigua Lake, New York, consist almost entirely of minute irregular, bush-like, micritic masses comparable with the calcareous alga Angulocellularia Vologdin from Lower Cambrian algal-arehaeocyathan bioherms and biostromes of the Siberian Platform and western Mongolia. The Recent specimens arc radially orientated within the oncoids and occasionally contain moulds of axial filaments 15 μm in diameter. Acid-residues of the oncoids yield abundant Schizothrix calcicola. The micritic bush-like masses are interpreted to have formed by the calcification of the sheaths of these cyanophytes. This analogue allows Angulocellularia to be reinterpreted as a calcified oscillatoriacean cyanophyte, rather than a rhodophyte as previously suggested. It indicates that filamentous cyanophytes can produce apparently solid calcareous fossils, not only porostromatc tubes. The occurrence of Angulocellularia has been overlooked in some previous studies of Cambrian and Ordovician bioherms. The generic diagnosis is emended. 相似文献